116 caster

[White Anthony <anthony.white@domain.elided>]

(Also posted to Alfa Racing.  Apologies for cross posting.)
 
Thanks to all those who replied to my query about 116 suspension tuning.
 
One thing continues to puzzle me, though.  A number of people noted that increasing the caster was one of the best ways to reduce understeer on a 116 chassis.  However, those who gave measurements suggested increasing caster to between 3 and 3.5 degrees positive.  My workshop manual (Haynes) lists 4.5 degrees positive as stock.   I understand anything above 6 degrees caster is starting to get unworkable.  Can anyone shed light on this?  Is the Haynes manual incorrect?  
 
Regards,
Anthony  
'85 116 Giulietta
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